1. Field of the Invention
This invention relates to vascular balloon catheters which may be used for percutaneous transluminal angioplasty procedures, or alternatively may be used to position and expand a reinforcing stent within a blood vessel. In particular, this invention is especially adapted to treatment of small diameter blood vessels within the brain and may, for example, be used to temporarily occlude a blood vessel to evaluate the results of the occlusion prior to placing a permanent occlusion device within the vessel.
2. Description of the Prior Art
Medical catheters exist for a wide variety of purposes, including diagnostic procedures and interventional therapy, such as drug delivery, drainage, and perfusion. Catheters for each of these purposes may be introduced to numerous target sites within a patient's body by guiding the catheter through the vascular system. A wide variety of specific catheter designs have been proposed for such different uses.
Of particular interest to the present invention, small diameter tubular access catheters are presently being used for diagnostic and interventional therapy techniques for vessels within the brain, such as the imaging and treatment of aneurysms, tumors, arteriovenous malformations, and fistulas. Such techniques place a number of requirements on the catheters that are to be employed. The primary requirement is size. The blood vessels in the brain are frequently as small as several millimeters, or less, requiring that catheters have an outside diameter as small as one French (0.33 millimeters). In addition to small size, the brain vasculature is highly tortuous, requiring that catheters used in vessels of the brain be very flexible, particularly at their distal ends, to pass through the regions of tortuosity. Additionally, the blood vessels of the brain are relatively fragile, so it is desirable that the catheters have a soft, non-traumatic exterior to prevent injury.
Balloon catheters are typically formed by bonding an inflatable balloon to a catheter body. Typically, the inflatable balloon is stiff, or non-compliant, and must be properly sized to avoid damaging the fragile blood vessels. The inflatable balloon section is usually thermally or chemically similar to the catheter body, allowing the bond to be formed using adhesive or thermal means. When the balloon is inflated, the construction of the non-compliant balloon causes most of the force to be applied to the inflatable section of the balloon rather than on the bond between the balloon and catheter body. On the other hand, balloons made of compliant materials reduce the need for precise sizing of the balloon. However, due to the chemical differences, adhesives do not form strong bonds between compliant materials, like silicone, and typical catheter-body materials, like polyurethane. When a compliant balloon is inflated, the force on the bond between the compliant balloon and catheter body causes the balloon to peel away from the catheter body. Eventually, the bond fails.
U.S. Pat. No. 4,850,348 to Pell et al., discloses an endotracheal tube with a cuff secured to the outer surface of the tube. The cuff is inflated by means of a pilot balloon connected to the cuff by an external tube and internal passage in the wall of the tube. The distal end of the cuff has an annular end that is secured in contact with the tube and faces in the direction of the proximal end of the tube. Thus, the annular end and distal radiopaque band are located interior to the cuff body.
U.S. Pat. No. 5,876,376 to Schwab et al., discloses a catheter balloon bonding stopper in which the stopper is used to prevent adhesive from wicking between the catheter body and the balloon tail into the balloon. U.S. Pat. No. 5,643,209 to Fugoso et al., discloses an adhesive bond between the inner surface of the distal tail of the balloon and the outer surface of the guidewire shaft. The adhesive bond continues as a filler beyond the balloon distal tip and gradually tapers distally to the same diameter as the outer diameter of the guidewire shaft step down portion.
U.S. Pat. No. 5,700,243 to Narcisco, Jr., discloses radiopaque bands used to crimp a balloon on a catheter shaft. U.S. Pat. No. 3,866,599 to Johnson, discloses clamping rings employed to attach an expandable sleeve to the body of a catheter.